Ray Next-Event Estimator Transport of Primary and Secondary Gamma Rays

This thesis investigated the application of the ray next event estimation Monte Carlo method to the transport of primary and secondary gamma rays. The problem of interest was estimation of the free field flux at a distant point in a vacuum from a point source in the atmosphere. An existing Fortran code for neutron transport, Ray Next-Event Estimator v4.0, was adapted to perform photon transport computations including coherent scattering, incoherent scattering, photoelectric absorption, and pair production interactions. Production and transport of secondary gamma rays produced in bremsstrahlung, neutron inelastic scatter, and neutron absorption interactions was also implemented. A new version of the code, Ray Next-Event Estimator v5.1, was produced with the added photon transport capability and other changes focused on future development of the estimator code for application to this class of problems. Code version 5.1 was exercised and compared to version 4.0 for neutron transport computations. Code version 5.1 was also demonstrated for application to gamma ray transport computations and coupled neutron-photon transport computations.